1. Field of the Invention
The present invention relates to satellite radio signal receiver that receives a radio signal from a positioning satellite to acquire date and time information, an electronic timepiece, a date and time information acquiring method and a recording medium.
2. Description of Related Art
There have been electronic timepieces (radio timepieces) that have a function of keeping their counting time correct by receiving a radio signal from a navigation satellite (positioning satellite) of the GNSS (Global Navigation Satellite System) and acquiring date and time information. Such radio timepieces do not require a user manual operation and can keep the counting and displaying date and time correct all over the world.
However, receiving a satellite radio signal places a load much greater than that of counting or displaying the date and time in an electronic timepiece. Accordingly, a problem with such radio timepieces is that a function of receiving a satellite radio signal requires a large battery, which results in the increased size and weight of the electronic timepiece. To cope with the problem, a variety of techniques for reducing power consumption have been developed.
One of such techniques for reducing power consumption is to reduce the reception time of a radio signal. For example, JP 2009-36748A, which is a Japanese patent document, discloses a technique of synchronizing signal reception with signal transmission of a predetermined part including the date and time information according to the format of the signal (navigation message) transmitted from GPS satellites. The signal reception is suspended while unnecessary information is being sent. At the time of the signal reception, to avoid false identification of the date and time, a parity data of the block including the predetermined part is acquired so that the integrity of the received data is checked.
However, decoding the date and time after identifying the code and then further performing a verification such as a parity check increases the processing load during the signal reception. Accordingly, a problem is that such techniques are likely to result in an increase in processing load and power consumption.